RunCommand: use IPC::Run3::run3 instead

run3 just seems to do better handling for what we want to do, and
requires less deep-reaching changes to this plugin to get it to play
nice, as IPC::Run::run would.

flake.nix

@@ -474,6 +474,7 @@
                 git
                 IOCompress
                 IPCRun
+                IPCRun3
                 JSON
                 JSONMaybeXS
                 JSONXS

src/lib/Hydra/Plugin/RunCommand.pm

@@ -10,7 +10,7 @@ use Hydra::Model::DB;
 use Hydra::Helper::Nix;
 use File::Basename qw(dirname);
 use File::Path qw(make_path);
-use IPC::Run;
+use IPC::Run3;
 
 sub isEnabled {
     my ($self) = @_;
@@ -178,9 +178,7 @@ sub buildFinished {
         open(my $f, '>', $logPath);
         umask($oldUmask);
 
-        my $stdin = "";
-        my @cmd = ["sh", "-c", $command];
-        IPC::Run::run(@cmd, \$stdin, $f, '2>&1') == 1
+        run3($command, \undef, $f, $f, { return_if_system_error => 1 }) == 1
             or warn "notification command '$command' failed with exit status $? ($!)\n";
 
         close($f);